The processing of lumber in modern sawmills requires the sawn boards to be transported on conveyors and, for some purposes, to be rotated while on the conveyor such that an unexposed lower face is inverted. For example, the optical scanning device disclosed in the present inventor's U.S. Pat. No. 5,412,220 provides two banks of scanners positioned above a conveyor, with the boards being processed by the scanner being rotated by 180 degrees about their longitudinal axes between the banks. Thus, the two banks are able to scan all four lateral faces of each board, without the need for any scanners to be positioned below the conveyor. For this and similar purposes, it is necessary to provide a means to rapidly and accurately invert lumber as it is transported along a conveyor.
Various means exist to invert boards and other objects being transported on conveyors. For example, U.S. Pat. No. 4,484,675 (Doherty et al.) discloses a board inverter that employs a pivot-mounted curved arm driven by a hydraulic cylinder. Upward movement of the arm inverts each board as it travels along the conveyor. Other patents that disclose board-turning devices include U.S. Pat. Nos. 3,887,066 (Houtsager); 4,029,196 (Eckholm); 4,936,437 (Gearhart). In these devices, actuation of the device typically requires a motor or other such drive means, such as the hydraulic cylinder of Doherty et al. These prior art devices are correspondingly complex to make, operate and repair, subject to periodic breakdowns, and may experience difficulty in operating at a sufficiently high speed to accommodate the high conveyor speeds of modern processing mills.
In order to provide a simple board inverter that is capable of operating at essentially any conveyor speed, it is desirable to utilize the forward motion of the boards themselves as the motive force to invert the boards. This eliminates the need for external drive means, with their attendant expense, complications, control requirements and speed limitations. In a simple such system, a rotating wheel receives boards as they travel along the conveyor, inverts each board, and replaces it on the conveyor, with the wheel being driven by the movement of the boards along the conveyor.